Vitamin B12
Vitamin B12 in tablets, capsules, sprays and drops, with methylcobalamin, cyanocobalamin and triple-form blends. We explain how the forms differ, why the doses run so high and who benefits most from taking B12 daily.Read more →
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Choosing a vitamin B12 supplement: forms, doses and absorption
What vitamin B12 is and where it comes from
Vitamin B12, also called cobalamin, is a water-soluble vitamin your body cannot make itself. It occurs naturally in meat, fish, eggs and dairy, and is added to foods such as fortified cereals and plant milks. Fruit, vegetables and grains contain none. Vitamin B12 contributes to normal energy-yielding metabolism and to the reduction of tiredness and fatigue. It also contributes to normal red blood cell formation and to the normal functioning of the nervous system. If you want the full picture across the group, our wider B vitamin range covers the other seven.
Why supplements contain far more than you need on paper
UK guidance sets 1.5 micrograms a day for adults aged 19 to 64, yet most single-nutrient products give 500 or 1000 micrograms. That gap is not marketing bravado, it follows how absorption works. Your gut takes up B12 with the help of a carrier protein called intrinsic factor, and that route handles only a few micrograms per dose. Above that ceiling, roughly one percent of the remaining amount crosses the gut wall passively. High-strength tablets are built around that second, inefficient route.
The four forms, and what actually separates them
- Cyanocobalamin: stable, the most studied, the lowest cost per microgram. Your body converts it into the active forms.
- Methylcobalamin: already active, so no conversion needed. Common in sprays and sublingual tablets.
- Adenosylcobalamin: the second active form, usually found in triple blends.
- Hydroxocobalamin: the storage form, used by the NHS in injections.
Be aware that the practical difference between these forms is smaller than the packaging suggests. Dose, consistency and whether you actually take it every day matter more than the suffix on the label.
How we choose the B12 we stock
We look at three things: the form, the dose and the combinations that make sense. We carry cyanocobalamin because it is stable and well documented, and active forms for people who prefer them, but we do not claim one is superior where the evidence does not show it. We prefer doses that match how B12 is absorbed: higher amounts in single-nutrient products, modest amounts inside a B-complex. We buy directly from the brands, and every product passes our compliance team before it goes live. See how we select brands and products.
Who a daily B12 genuinely suits
The clearest case is a plant-based diet, since no unfortified plant food supplies B12. You will find B12 among our supplements suitable for a vegan diet. Absorption also tends to decline with age, which is why many people over 60 keep a supplement going. Long-term use of certain medicines can lower B12 levels too, so speak to your GP if that applies to you.
B12 is often taken alongside folate, also known as vitamin B9, because both are involved in red blood cell formation. One honest caveat: if your levels are already fine, a supplement will not add extra energy. It fills a gap rather than creating a surplus, and blood levels usually take several weeks of daily use to move.
Frequently asked questions
Vitamin B12, or cobalamin, is a water-soluble vitamin found in animal foods such as meat, fish, eggs and dairy, and in fortified foods. Your body cannot produce it, so it has to come from your diet or a supplement. It contributes to normal energy-yielding metabolism, the reduction of tiredness and fatigue, normal red blood cell formation and normal psychological function. People usually supplement because their diet supplies little B12, or because their body absorbs less of it than it used to.
UK and European reference figures differ, because they are set in different ways. The UK figure is the amount that covers almost everyone in the population; the European figure is an adequate intake based on markers of B12 status.
| Reference | Group | Per day |
|---|---|---|
| NHS (UK) | Adults 19 to 64 | 1.5 µg |
| EFSA | Adults | 4 µg |
| EFSA | Pregnancy | 4.5 µg |
| EFSA | Breastfeeding | 5 µg |
Supplement doses are much higher because only a fraction of a large dose is taken up.
Source: NHS, EFSAAll four forms end up doing the same job in your body. Choose on price, on whether you want an active form, and on how you like to take it.
| Form | Active? | Typical use |
|---|---|---|
| Cyanocobalamin | No, converted | Tablets, low cost |
| Methylcobalamin | Yes | Sprays, sublingual |
| Adenosylcobalamin | Yes | Triple blends |
| Hydroxocobalamin | Storage form | Blends, injections |
If you have no preference, cyanocobalamin is the most studied and the cheapest per microgram.
Any time of day works, because B12 is water-soluble and does not need fat to be absorbed. Most people take it in the morning with breakfast, simply because a fixed moment makes it easier to remember. Consistency matters more than timing. If you take a high-dose tablet, splitting it is not necessary; a single daily dose is fine. Sublingual tablets and sprays are best held in the mouth for a short while before swallowing.
B12 has a low risk of excess because it is water-soluble and surplus amounts leave the body in urine. Even so, the NHS advises staying at 2 mg (2000 µg) a day or less from supplements, and notes there is not enough evidence on the effects of very high daily doses over time. In practice, a 500 to 1000 µg product sits well inside that. Do not exceed the dose on the label.
They are often promoted as bypassing the digestive system, but the research is not conclusive. Some B12 is taken up through the lining of the mouth, while a large part of the dose is still swallowed with saliva and absorbed in the gut like any tablet. The real advantage is practical: sprays and drops suit anyone who dislikes swallowing tablets, and they are easy to give to older family members.
Blood levels start to rise within days, but how you feel is a different question. If your intake was genuinely low, expect several weeks of consistent daily use before any change in tiredness becomes noticeable, and longer if your stores were depleted. If your levels were already adequate, extra B12 will not add energy on top. For broader support around tiredness, see our energy support selection.
Yes, in practice. The 1.5 µg figure assumes B12 spread across meals from food, where uptake is relatively efficient. With a single daily supplement, the intrinsic factor route saturates and only a small share of the dose is absorbed. The British Dietetic Association therefore advises people on a plant-based diet to take at least 10 µg daily, or 2000 µg once a week, alongside fortified foods such as plant milks and yeast extract.
Follow the medical route in that case. Injections are used when the problem is absorption rather than intake, for example with pernicious anaemia or after certain stomach or bowel surgery, because the gut cannot take up enough B12 whatever the dose. Food supplements are made for topping up intake, not for treating a diagnosed deficiency. If you have tingling in the hands or feet, persistent fatigue or memory changes, see your GP before self-supplementing.
